The present invention relates to a data processing system in which a first data-processing device such as a portable terminal unit can be attached to a second data-processing device so that the first data-processing device is used as a part of an operating section of the second data-processing device, and more particularly, to a data processing system wherein the second data-processing device can stably supply the first data-processing device with a stabilized power in the controlled state.
A known example of a second data-processing device for executing data-processing operation according to processing data input through an operating section is a digital color copying machine that performs specified processing operations on data of an original color image input through an image-inputting unit such as a scanner, then outputs the original color image reproduced according to the processed image data through the color printer section.
Japanese Laid-Open Patent Publication No. 5-145673 discloses a data-processing system for a digital color copying machine, which system allows the copying machine to work by processing data according to parameters preset and input from the second operating means such as an external universal personal computer or the like. Furthermore, Japanese Utility Model Publication No. 2-6451 discloses a copying machine that has a removable operating portion and works according to the operation mode and data preset in the operating portion.
Till now, there been thus proposed data-processing systems each consisting of two separate data-processing devices, one (the second) of which performs data-processing operation according to processing data (operating mode data) input from the other (first) device. The first device, which is an external device to the second device, may be a so-called mobile computer.
However, the conventional image processing systems have no consideration of power supply problem for first and second data-processing devices from the view point of saving in power consumption and protecting data in the first data-processing device. Particularly, a data-processing system in which the first data-processing device is a portable terminal operating always on its inner battery for transmitting the data to the second data-processing device, cannot operate for a long time due to the battery capacity of the first device.
An attempt to solve the above problem by supplying power from the second data-processing device to the portable terminal arises another problem that data stored in the terminal may be broken by unintentional disconnection between the data-processing device and the terminal due to unmatched stating and ending procedures at both devices.